In the past, little attention was paid to the storage or recycling of refrigerant. When refrigeration systems were being repaired or when the refrigerant, such as those sold under the trademark "Freon," was contaminated sufficiently to affect the effectiveness of refrigeration, the refrigerant was vented into the atmosphere.
Recent developments have, however, created a demand for systems capable of storing refrigerant while at the same time purifying the contaminated refrigerant. The United States, as have several other countries, has become a signatory of the "Montreal Protocol on Substances that Deplete the Ozone Layer", which restricts future productions of fully halogenated chlorofluorocarbons. Pursuant to this international mandate, future production of all currently used refrigerants are to be drastically cut by the end of the century. In addition to this development, the United States Environmental Protection Agency has classified several widely used refrigerants as hazardous substances under the Resource Conservation and Recovery Act ("RCRA").
The combination of these two regulatory developments accentuates the necessity for a device which will store and purify refrigerant, eliminating the possibility of unlawful emissions and the necessity for purchasing refrigerants in an artificially constrained market. The present invention relates to improvements on the refrigerant reclaim method and apparatus as described in co-pending U.S. application Ser. No. 109,958 of Van Steenburgh, Jr.
Patent application Ser. No. 109,958, discloses an apparatus for drawing refrigerant from a container, or a refrigeration system to be repaired, heating the refrigerant sufficiently to maintain it in a gaseous state while it passes through an oil separator into the intake of a compressor. Compressed gaseous refrigerant is discharged from the compressor and passed through a heat exchanger to heat the incoming liquid refrigerant and then passes through to a condenser where it is liquefied. The liquefied refrigerant is passed from the condenser into a hold tank from the bottom of which liquid refrigerant flows through a filter-dryer and an expansion device for reconverting the liquid refrigerant to a gaseous form. From the expansion device the gaseous refrigerant passes through a coil submerged in the liquid in the hold tank and then is passed back to the intake of the compressor. The temperature of the liquid in the hold tank is lowered by the chilling effect of the expanding gaseous refrigerant passing through the coil submerged in the liquid. The refrigerant can be repeatedly passed from the chill tank through the filter-dryer, expansion device, cooling coil, compressor, heat exchanger, condenser and back to the hold tank. This repeated process will progressively lower the temperature of refrigerant in the hold tank, pass the refrigerant through the filter-dryer repeatedly, and, by lowering the temperature of the refrigerant, maximize the separation of air from the refrigerant.
The apparatus described in application Ser. No. 109,958 provides several advantages over the prior art. There are, however, several additional attributes that are desirable in refrigerant reclaim systems.
One of the major deficiencies in the apparatus described in application Ser. No. 109,958, as well as in other refrigerant reclaim devices, is in the removal and reclamation of various refrigerants. U.S. application Ser. No. 258,166, also a continuation-in-part of application Ser. No. 109,958, describes means for utilizing the refrigerant reclaim system with a plurality of different refrigerants. Because of the different physical properties of different refrigerants, it is necessary to utilize different expansion valves for each refrigerant. Application Ser. No. 258,166 describes an apparatus for switching different expansion valves on-line based on the particular refrigerant being reclaimed.
Along with the great advantages of being able to use a single reclamation unit for several different refrigerants, is an associated problem. After discharging liquefied and chilled refrigerant from the chill-tanks of the reclaim unit, the system still contains a significant amount of refrigerant vapor. This vapor can be at a pressure from 80 to 150 psi and can total 2 to 8 pounds of refrigerant. When the next refrigeration system to be reclaimed contains the same refrigerant, the vapor can be left in the reclaim unit. However, when a different refrigerant is to be reclaimed, the refrigerant vapor must be removed from the system. It is very important that different refrigerants not be mixed together.
The traditional response to such a problem would be to vent the refrigerant to the atmosphere. Unfortunately, as described above, the venting of relatively significant amounts of refrigerant is no longer a viable alternative. In the device disclosed in application Ser. No. 109,958, venting is accomplished by opening both the inlet and outlet valves and letting the refrigerant escape from the different sections of the system. Opening just the inlet or outlet would not allow all the gaseous refrigerant to be released. Means for quickly removing residual refrigerant vapor from the reclaim unit are quite necessary and currently unavailable in existing reclaim systems.
An additional problem with the refrigeration reclaim system described in application Ser. No. 109,958 is in the maintenance of the compressor motor. Application Ser. No. 258,166 describes means for cooling the motor windings and for monitoring crankcase oil levels.
During long term use of the refrigerant reclaim system of application Ser. No. 109,958, it is clear that the vast majority of oil entering the reclaim system with the refrigerant is separated out in the oil separator. Some residual oil is still seen in the refrigerant even after several passes through the evaporation/condensation process. The presence of small residual amounts of oil in the refrigerant is predominantly attributable to the gradual loss of oil from the crankcase of the compressor. It is, therefore, desirable to find some means of removing the residual oil from the refrigerant and returning it to the compressor.
A final problem associated with all refrigeration reclaim systems is the design of high pressure seals at the systems inlet and outlet ports. For example, at the refrigerant inlet port, it is necessary to have a seal or valve that will allow refrigerant to flow into the system from a high pressure source. At the same time, the seal or valve must be capable of preventing the loss of high pressure refrigerant from within the system. The opposite set of circumstances causes a similar problem at the outlet of the system. The problem with solving what sounds like a relatively simple problem, is that there is no commercially available refrigeration valve capable of stopping flow in two directions when closed.